Examples of an image scanning apparatus capable of scanning an original sheet placed on a platen are a complex printer, a copying machine, a facsimile transmitter, etc. Some of these image scanning apparatuses are provided with an original sheet cover to which a white film is bonded to prevent a surrounding region of an original sheet having a smaller area than a platen from being printed in black color, when scanning the original sheet to print an image on a recording medium such as a sheet of recording paper. The original sheet cover serves to support the original sheet to be scanned.
An area of the original sheet capable of being scanned in one scanning process is limited. In some cases, it is necessary to scan a part of the original sheet having a larger area. In these cases, a part of the original sheet placed on the platen protrudes from the platen and hangs therefrom. The original sheet is likely to be displaced from a correct position because of weight of the protruding portion hanging from the platen. To avoid this, an operator closes the original sheet cover and holds the original sheet while pressing the original sheet with a hand. The operator must release the hand from the original sheet before the original sheet cover has been completely closed. Still, the original sheet is likely to be displaced from the correct position.
Accordingly, Japanese Laid-Open Patent Application Publications Nos. 2006-78516 and 2000-321683 disclose image scanning apparatuses configured to scan a part of an original sheet having a relatively large area while maintaining the original sheet in a correct position. In these image scanning apparatuses, a support portion which is substantially coplanar with a platen is provided to support a surface of a protruding portion of the original sheet placed on the platen. This eliminates a need for the operator to press the original sheet with a hand when closing an original sheet cover, suppressing displacement of the original sheet.
Because of limited installation areas or transportability associated with changing of interiors, it is demanded that image scanning apparatuses such as complex printers commonly used at home and the like or copying machines and facsimile transmitters widely available at offices have a smaller size. In the image scanning apparatuses disclosed in the above Publications, since the support portion supports the surface of the protruding portion of the original sheet, it is necessary to protrude the support portion with a large amount horizontally from a main body of the apparatus such that the support portion is made substantially coplanar with the platen. In addition, the whole original sheet supported by the support portion, including the protruding portion is caused to have a horizontal posture. This increases the size of the apparatus including the support portion, and therefore makes it difficult to meet the above demand.